vasprintf.c revision 21673 
1/*-
2 * Copyright (c) 1996  Peter Wemm <peter@freebsd.org>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26#if defined(LIBC_RCS) && !defined(lint)
27static char rcsid[] = "$FreeBSD: head/lib/libc/stdio/vasprintf.c 21673 1997-01-14 07:20:47Z jkh $";
28#endif /* LIBC_RCS and not lint */
29
30#include <stdio.h>
31#include <stdlib.h>
32
33#if __STDC__
34#include <stdarg.h>
35#else
36#include <varargs.h>
37#endif
38
39#define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */
40
41struct bufcookie {
42	char	*base;	/* start of buffer */
43	size_t	size;
44	size_t	left;
45};
46
47static int 	writehook __P((void *cookie, const char *, int));
48
49static int
50writehook(cookie, buf, len)
51	void *cookie;
52	const char *buf;
53	int   len;
54{
55	struct bufcookie *h = (struct bufcookie *)cookie;
56	char *newbuf;
57
58	if (len == 0)
59		return 0;
60
61	if (len > h->left) {
62		/* grow malloc region */
63 		/*
64		 * XXX this is linearly expanded, which is slow for obscenely
65		 * large strings.
66		 */
67		h->left = h->left + len + CHUNK_SPARE;
68		h->size = h->size + len + CHUNK_SPARE;
69		newbuf = realloc(h->base, h->size);
70		if (newbuf == NULL) {
71			free(h->base);
72			h->base = NULL;
73			return (-1);
74		} else
75			h->base = newbuf;
76	}
77	/* "write" it */
78	(void)memcpy(h->base + h->size - h->left, buf, (size_t)len);
79	h->left -= len;
80	return (len);
81}
82
83
84int
85vasprintf(str, fmt, ap)
86	char **str;
87	const char *fmt;
88	va_list ap;
89{
90	int ret;
91	FILE *f;
92	struct bufcookie h;
93
94	h.base = malloc(CHUNK_SPARE);
95	if (h.base == NULL)
96		return (-1);
97	h.size = CHUNK_SPARE;
98	h.left = CHUNK_SPARE;
99
100	f = funopen(&h, NULL, writehook, NULL, NULL);
101	if (f == NULL) {
102		free(h.base);
103		return (-1);
104	}
105	ret = vfprintf(f, fmt, ap);
106	fclose(f);
107	if (ret < 0) {
108		free(h.base);
109		return (-1);
110	}
111	if (h.base == NULL)	/* failed to realloc in writehook */
112		return (-1);
113
114	h.base[h.size - h.left] = '\0';
115	*str = realloc(h.base, (size_t)(h.size - h.left + 1));
116	if (*str == NULL)	/* failed to realloc it to actual size */
117		*str = h.base;	/* return oversize buffer */
118	return (ret);
119}
120